A double arene hydroxylation mediated by dicopper(II)-hydroperoxide species
A double arene hydroxylation mediated by dicopper(II)-hydroperoxide species
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DOI：
10.1021/ja0280776
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发表时间：
2003-04-09
影响因子：
15
通讯作者：
Tuczek, F
中科院分区：
文献类型：
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作者：
Battaini, G;Monzani, E;Tuczek, F
将二铜（II）配合物[Cu-2（L）]（4+）（L = α，α ′-双{双[2-（1 '-甲基-2'-苯并咪唑基）乙基]氨基}-间二甲苯）与过氧化氢反应得到二铜（II）-对苯二酚配合物，其中配体的二甲苯基环在环2和5位发生双羟基化反应。通过分解产物络合物分离出二羟基化配体2，6-双（{双[2-（3-甲基-H-1-苯并咪唑-2-基）乙基]氨基}甲基）苯-1，4-二醇。通过使用（H2 O2）-O-18的同位素标记研究证实了来自H2 O2的两个氧原子并入配体中。通过制备L的两种异构体酚衍生物，即3，5-双（{双[2-（1-甲基-H-苯并咪唑-2-基）乙基]氨基}甲基）苯酚（6）和2，6-双（{双[2-（1-甲基-1H-苯并咪唑-2-基）乙基]氨基}甲基）苯酚（7），研究了不寻常的双羟基化途径，其中L被羟基化的两个位置之一带有羟基。用新配体6和7制备的并含有桥接μ-苯氧基部分的双铜（II）配合物在羟基化中是无活性的。然而，衍生自6并含有质子化苯酚的双铜（II）络合物3被H2 O2快速羟基化，并且代表[Cu-2（L）]（4+）羟基化中形成的第一产物。对[Cu-2（L）]（4+）和3与H2 O2反应的动力学研究表明，在室温下，第二次羟基化反应比第一次快（0.13 +/- 0.05 s（-1）vs 5.0（+/-0.1）x 10（-1）s（-1）），且均为分子内反应.然而，这两个反应表现出不同的活化参数（DeltaH（双刃）= 39.1 +/- 0.9 U mol（-1），DeltaS第一次羟基化的（双匕首）= -115.7 +/- 2.4 J K-1 mol（-1）;对于第二次羟基化，DeltaH（双匕首）= 77.8 +/- 1.6 kJ mol（-1）和DeltaS（双匕首）= -14.0 +/- 0.4 JK-1 mol（-1））。通过研究[Cu-2（L）]（4+）和H2 O2在低温下的反应，我们能够表征中间体eta（1）：eta（1）-氢过氧二铜（II）加合物在第一羟基化步骤中的活性，[Cu-2（L）（OOH）]（3+）[λ（max）= 342（λ 12 000），444（λ 1200）和610 nm（λ 800 M-1 cm（-1）;冷冻溶液中的宽EPR信号指示磁耦合Cu（II）中心]。
The dicopper(II) complex [Cu-2(L)](4+) (L = alpha,alpha'-bis{bis[2-(1'-methyl-2'-benzimidazolyl)ethyl]amino}-m-xylene) reacts with hydrogen peroxide to give the dicopper(II)-hydroquinone complex in which the xylyl ring of the ligand has undergone a double hydroxylation reaction at ring positions 2 and 5. The dihydroxylated ligand 2,6-bis({bis[2-(3-methyl-H-1-benzimidazol-2-yl)ethyl]amino}methyl)benzene-1,4-diol was isolated by decomposition of the product complex. The incorporation of two oxygen atoms from H2O2 into the ligand was confirmed by isotope labeling studies using (H2O2)-O-18. The pathway of the unusual double hydroxylation was investigated by preparing the two isomeric phenolic derivatives of L, namely 3,5-bis({bis[2-(1-methyl-H-benzimidazol-2-yl)ethyl]amino}methyl)phenol (6) and 2,6-bis({bis[2-(1-methyl-1H-benzimidazol-2-yl)ethyl]amino}methyl)phenol (7), carrying the hydroxyl group in one of the two positions where L is hydroxylated. The dicopper(ll) complexes prepared with the new ligands 6 and 7 and containing bridging mu-phenoxo moieties are inactive in the hydroxylation. Though, the dicopper(II) complex 3 derived from 6 and containing a protonated phenol is rapidly hydroxylated by H2O2 and represents the first product formed in the hydroxylation of [Cu-2(L)](4+). Kinetic studies performed on the reactions of [Cu-2(L)](4+) and 3 with H2O2 show that the second hydroxylation is faster than the first one at room temperature (0.13 +/- 0.05 s(-1) vs 5.0(+/-0.1) x 10(-1) s(-1)) and both are intramolecular processes. However, the two reactions exhibit different activation parameters (DeltaH(double dagger) = 39.1 +/- 0.9 U mol(-1) and DeltaS(double dagger) = -115.7 +/- 2.4 J K-1 mol(-1) for the first hydroxylation; DeltaH(double dagger) = 77.8 +/- 1.6 kJ mol(-1) and DeltaS(double dagger) = -14.0 +/- 0.4 J K-1 mol(-1) for the second hydroxylation). By studying the reaction between [Cu-2(L)](4+) and H2O2 at low temperature, we were able to characterize the intermediate eta(1):eta(1)-hydroperoxodicopper(II) adduct active in the first hydroxylation step, [Cu-2(L)(OOH)](3+) [lambda(max) = 342 (epsilon 12 000), 444 (epsilon 1200), and 610 nm (epsilon 800 M-1 cm(-1)); broad EPR signal in frozen solution indicative of magnetically coupled Cu(II) centers].